1. Field of the Invention
The present invention relates to a display apparatus and a control method thereof. More particularly, the present invention relates to a display apparatus capable of decreasing a motion blur and a control method thereof.
2. Description of the Related Art
The cathode ray tube (CRT) has recently been replaced with new display systems. As an example of alternatives to the CRT, there is a liquid crystal display (LCD) which is being applied to televisions, computer monitors, and the like. Compared to the CRT, the LCD is relatively thin, flat and lightweight.
The CRT and the LCD are significantly different in their driving methods. In a CRT, very short light flashes are generated by phosphors and each image is displayed in a very small part of one frame period, which is called an impulse-type display. On the other hand, the LCD has a sample and hold characteristic that displays one image with the same red, green and blue (RGB) brightness maintained throughout the entire frame period, which is called a hold-type display.
LCDs have a motion blur problem because it has a long response time and the characteristic of the hold-type display. To fundamentally make the response time of the LCD faster, liquid crystal material and a cell design should be optimized. Currently, a kind of overdrive method based on a lookup table (LUT) has been adopted to alleviate the long response time problem. The overdrive method accelerates the response time of the liquid crystal. At present, many LCD panels can limit a gray level response time to 8 ms or below.
However, a motion blur remains in the LCD due to its characteristic of the hold-type display even though the response time approximates 0. To reduce the motion blur due to the characteristic of the hold-type display, various methods have been proposed.
In a straightforward method, an additional frame is inserted per two frames, thereby decreasing a frame period. However, this method requires that the additional frame inserted corresponding to an original frame should be predicted. Therefore, motion estimation and motion compensation are necessary for estimating the additional frame. This method is called a motion estimation and motion compensation (MEMC) method. However, due to prediction requirement this method is relatively difficult, and requires additional hardware components to implement.
Further, in a motion-compensated inverse filtering (MCIF) method, a motion blur is decreased without increasing a frame period. However, a low pass filter for a motion blur is a zero cross filter, so that it is practically impossible to implement an ideal inverse filter. In the MCIF method, a high frequency boost method is used in estimating an ideal inverse low pass filter, but an overshoot problem arises. Further, the MCIF method requires additional motion vector estimation hardware to be designed and implemented.
Also, there is a black insertion method for decreasing the motion blur due to the characteristic of the hold-type display. In the black insertion method, an output video frame has a period having half the duration of an input video frame. That is, two video frames are output in one period of an input video frame, and the two video frames include a first half frame corresponding to the input video frame, and a second half frame filled with the black signal. However, this black insertion method has a problem of low brightness. To enhance the brightness of a backlight module, the brightness must be compensated, but there arises problems in that a display panel should be redesigned and the temperature of the backlight module rises in order to compensate the brightness of the backlight module. The gray level of the first half frame between two frames can be doubled to maintain the brightness, but causes problems due to a gray level limit (0 through 255).